Remove ShardingSphere Agent support for Zipkin exporter

## Feature Request

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### Is your feature request related to a problem?

- See https://github.com/apache/shardingsphere/pull/37717 .

### Describe the feature you would like.

- The `io.opentelemetry:opentelemetry-exporter-zipkin` is deprecated and unmaintained. It doesn't even align with the dependencies of `open-telemetry/opentelemetry-java`, leading to the conclusion that everyone should only use OTLP. See https://github.com/open-telemetry/opentelemetry-specification/pull/4715 , https://opentelemetry.io/blog/2025/deprecating-zipkin-exporters/ and https://github.com/open-telemetry/opentelemetry-java/issues/7863 .
- Incidentally, Zipkin also supports OTLP. See https://github.com/openzipkin-contrib/zipkin-otel/blob/main/module/README.md . Developers can continue to pass data to Zipkin via `io.opentelemetry:opentelemetry-exporter-otlp`.

> At least for Java, the zipkin exporter uses dreprecated attributes and lacks resource attributes. If users want to send trace signals to Zipkin, they should use the otlp collector from zipkin-otel.

- I believe we should remove the use of `io.opentelemetry:opentelemetry-exporter-zipkin`. This includes removing all related documentation and unit tests, integration tests, and E2E tests.